Power hand tool for die finishing and the like



Nov. 7, 1961 M, J. RIEDL 3,007,230

POWER HAND TOOL FOR DIE FINISHING AND THE LIKE Filed Dec. 3, 1959 557 '7IN VEN TOR.

93 Max J. RIEDL.

BY l3 9 0,14,4 ,14,

A'r'rvs.

tive lubrication arrangement.

United States Patent Q 3,007,230 POWER HAND TOOL FOR DIE FINISHING ANDTHE LIKE Max J. Riedl, Nor-ridge, 111., assignor to Acme ScientificCompany, Chicago, 111., a corporation of Illinois Filed Dec. 3, 1959,Ser. No. 857,045 2 Claims. (Cl. 29-46) The present invention relates topower hand tools and more particularly to a filing tool for smoothingand polishing surfaces of dies and the like.

In making dies for molding plastic and metal, the finish of the finalproduct depends upon the finish imparted to the surface of the dieitself. This finish is commonly achieved by skilled operators employinga tool for reciprocating small blocks of abrasive of various grades. Diefinishing is a tedious and exacting procedure requiring a tool whichmeets a number of specialized requirements.

It is an object of the invention to provide a filing tool of thereciprocating type which is variable in stroke over wide limits butwhich is nevertheless dynamically balanced for all stroke adjustments soas to produce a minimum amount of vibration. In this connection it is anobject to provide a tool which may be employed universally regardless ofthe grade of abrasive or length of stroke required and which may be usedfor hours at a time, for example, over an entire shift, without operatorfatigue. It is a more specific object to provide a filing tool in whichthe balancing counterweights are automatically adjusted incident tosetting the stroke adjustment so that both the adjustment and operationof the tool are simple and foolproof.

With regard to setting the stroke, it is an object to provide a filingtool which includes a novel and convenient adjusting arrangement havinga calibrated scale and in which the tool is automatically placed in areference condition incident to inserting an adjusting tool therebyinsuring a correct scale reading.

It is another object of the invention to provide a novel filing toolwhich is safe to use and which does not provide any hazard to theoperator or the workpiece even when carelessly handled. Morespecifically, it is an object to provide a tool in which all of thevibrating parts are enclosed and in which the only exposed vibratingelement is the file itself at the tip of the tool. In this connection itis an object to provide a filing tool which, although it providespositive driving of the filing element, nevertheless includes a novelyielding connection which gives in the event that the file strikes ashoulder or other portion of the workpiece on its forward power stroke.Thus it is an object of the present invention to provide a tool of theabove type which is self protecting and in which parts cannot be bent oroverloaded.

It is still another object of the present invention to provide a filingtool which is extremely durable and which may be operated for longperiods of time at a greater loading than conventional tools ofcomparable size and weight. More specifically, it is an object toprovide a tool which avoids the points of inherent weakness of the toolswhich have been used for this purpose in the past. It is accordingly anobject to provide a filing tool which has a longer useful life, with aminimum of maintenance, than conventional tools.

It is still another object of the present invention to pro vide a filingtool which is easily disassembled for periodic cleaning and inspectionand which has a novel and efiec- Finally it is an object to provide afiling tool which has a small number of moving parts and which does notrequire any critical machining operations. Consequently, it is an objectto provide a tool which may be inexpensively constructed and capable ofuse with flexible shafts or any other conveniently available drivingmeans.

Other objects and advantages of the invention will become apparent fromthe attached detailed description and upon reference to the drawings inwhich:

FIGURE 1 is a longitudinal section taken along the axis of the tool.

FIG. 2 is a transverse section taken along the line 2-2 in FIG. 1.

FIG. 3 is a fragmentary cross section taken along the line 33 in FIG. 1showing the tool adjusted for the maximum stroke condition.

FIG. 4 is a cross section similar to FIG. 3 but showing the minimum(zero) stroke condition.

FIG. 5 is a fragmentary top View of the tool with the cap removedshowing the scale and setting used for the maximum stroke condition ofFIG. 3.

FIG. 6 is a fragmentary section showing the lubricating arrangement.

While the invention has been described in connection with a preferredembodiment, it will be understood that I do not intend to be limited tothe particular embodiment shown but intend to cover the other equivalentand alternative constructions included within the spirit and scope ofthe appended claims.

Referring now to the drawing, a tool constructed in accordance with thepresent invention is indicated in axial cross section at 10. It includesa hollow cylindrical frame or shell 11 having a cap 11a and defining acentral space 12. Extending centrally within the tool is a shaft 13mounted in ball bearings 14, 15 which are spaced from one another atopposite ends of the chamber 12. To perrnit access, the upper ballbearing 15 is mounted in a threaded annular bushing 16 which is screwedinto the upper end of the frame.

For the purpose of driving the shaft 13, a flexible shaft 20 is usedhaving a central rotatable cable 21 connected to an electric motor orthe like. Preferably the flexible shaft 20 is coupled to the tool by acoupling having a sleeve portion 22 and an insert portion 23. The sleeveportion 22 may be integral with the frame 11, or it may be, as shown, aseparate tubular piece which surrounds the shaft 13 and which is screwedonto the lower end of the frame. To maintain the inserted portion of thecoupling in place, a ball detent 25 is used which is seated in anaperture in the sleeve 22 and which is held therein by means of anencircling 0 spring 26. A bayonet connection '28 is provided between thecentral drive cable 21 and the lower tip of the shaft 13. Simply stated,when the insert 23 is slipped into its detented position, a drivingconnection is made with the power source permitting the tool to befreely manipulated.

Extending at right angles away from the frame 11 is a tubular offset 39.Such ofliset is preferably screwed into the side of the frame 11 asshown. Slidably mounted in the offset 30 is a slide 31 which includes achuck 32 and a shank portion 33. For clamping a tool in the chuck, asetscrew 34 is provided, access being had through an aperture 35normally covered by an encircling 0 spring 36.

Received in the chuck 32 is a filing tool 40 having an offset shankmounting a file in the form of abrasive block 41. The latter is broughtto bear against the surface of the workpiece fragmentarily indicated at42. In the illustration, the file is shown seated on the bottom of acavity; in normal use, the file reciprocates back and forth in thedirection of the arrows, finishing and polishing the surface tomirror-like appearance.

For counteracting the unbalance of the slide, a counterweight 45 isfixed to the shaft by a setscrew 46.

In accordance with the present invention a novel eccentric and pitmanarrangement is employed between the drive shaft 13 and the slide 31 forvarying the length of the stroke of the slide and for simultaneouslyvarying the amount of counterweighting so that the effectivecounterweight is at all times proportioned to the length of the stroke.This is accomplished in the present instance by providing on the shaft13 an eccentric 50 which is surrounded by a pitman 51. This pitman ispreferably of two piece construction as shown having a pitman rod 52which is screwed into the pitman at its inner end and which engages theslide 31 at its outer end. Interposed between the eccentric 50 and thering of the pitman 51 is an eccentric sleeve 55. The latter is soconstructed that its eccentricity adds to the eccentricity of theeccentric 50 to provide a maximum throw in one phase position andsubtracts from, or neutralizes, the eccentricity of the ccentn'c 50 toprovide a condition of minimum or zero throw when twisted around theshaft through 180.

In order to adjust the phase position of the eccentric sleeve 55 and atthe same time change the degree of counterweighting, an adjustablecounterweight 60 is provided having a keyed connection with theeccentric sleeve 55. This keyed connection is, in the present instance,brought about by machining on the sleeve 55 an axial projection 56 andby notching the counterweight 60 to form a notch 61 which snuglyembraces the key 56. Being thus keyed together, it will be apparent thatthe eccentric sleeve 55 and the counterweight 60 always have the samephase relationship to one another so that when one of the elements ismoved to a new phase position with respect to the drive shaft 13, theother will be correspondingly moved.

In accordance with one of the aspects of the invention means areprovided for adjusting the shaft 13 with respect to the sleeve 55 andcounterweight 60 with the latter maintained at a reference position withrespect to the frame of the tool, and means are further provided on theshaft and frame for indicating the phase position of the shaft withrespect to the frame which exists at the time that the adjusting meansis tightened. In the present instance the counterweight 60 is clamped ina desired phase position on the shaft by means of a setscrew 62, and anarrow opening 65 is formed in the wall of the hollow frame throughwhich an appropriate tool such as an Allen wrench or the like 66 may beinserted. Thus, insertion of the tool through the aperture 65 and intothe setscrew insures that the eccentric collar 55 and counterweight 60occupy a predetermined reference position so that the degree ofeccentricity and hence the stroke of the tool is indicated by the thenexisting phase position of the shaft with reference to the frame of thetool.

In order to provide direct reading of the throw, a scale 70 is providedat the top of the tool mounted upon the annular bushing 16. Cooperatingwith this scale 70 is a pointer 71 which may simply be a line inscribedon the side of the shaft. The scale 70 as noted in FIG. is marked olfdirectly in terms of throw, from zero to A".

The function of the mechanism and indicia described thus far will beapparent upon reviewing a typical adjustment of the tool. Suppose it isdesired to set up the condition of maximum throw. The cap 11a of thetool is removed exposing the end of the shaft 13 as wel as the scale 70.The end of the shaft is machined to be hexagonal as indicated at 73 sothat it may be engaged by an open end wrench of the like. The Allenwrench or other adjusting tool 66 is then inserted into the opening 65,and the shaft 13 is rotated either manually or by the shaft wrench untilthe tool 66 falls into seated position in the set screw 62. The tool 65is then turned to unscrew the set screw and hence to release theeccentric sleeve 55 and its associated counterweight 60 from the shaft.The shaft wrench is next turned so that the pointer 71 thereon isrotated around into the position shown in FIG. 5, i.e., the position for4" throw. The tool 66 is then turned to screw the setscrew tight ontothe shaft thereby to lock the eccentric sleeve 55 in its position ofmaximum throw, i.e., the position where its throw is additive withrespect to the throw of the eccentric 50 on the shaft. It will be notedthat under such conditions the counterweight 60 and the counterweight 45are alined with one another so that their effects are additive. Thus thecondition of maximum throw is accompanied by maximum effectivecounterweighting.

It will next he assumed that the tool is to be adjusted for a very smallthrow of say, only of an inch. The adjusting operation is then repeatedas follows: The tool 66 is inserted and the shaft 13 is rotated untilthe tool is seated in position in the set screw 62, thereby establishingthe reference position of the essentric sleeve and the associatedcounterweight with respect to the frame. The set screw is loosened and,keeping the tool 66 in place, the shaft 13 is turned until the mark 71thereon is opposite the inch position of the scale 70. Either one of thetwo available positions may be employed. The set screw is thentightened, following which the tool 66 may be withdrawn. Under suchconditions the eccentric sleeve will be rotated around to nearly theposition shown in FIG. 4 where the eccentricity of the eccentric 50 andthe sleeve 55 almost cancel out thereby producing a nearly Zero stroke.Also under such conditions, the counterweight 6ft is rotated withrespect to the counterweight 45 so that the two are opposite oneanother, providing a condition of minimum counteiweighting correspondingto the minimum stroke. It will be apparent to one skilled in the artthat intermediate conditions of adjustment are possible and that thehalf-way condition of the eccentric sleeve will be accompanied by ahalf-way condition of the counterweight.

It is of interest to note that rotation of the counterweight 60 relativeto the shaft not only changes the stroke and the amount of effectivecounterweighting but also maintains the direction of the counterweightvector in a direction opposite to the direction of unbalance. This isdue to the fact that rotation of the sleeve 55 changes the effectiveangle of the cam 50.

In accordance with one of the more detailed features of the constructiona yieldable connection is provided between the pitman and the slide sothat in the event the file is obstructed in its forward stroke, as willoccur when the tool advances too closely to a shoulder on the workpiece,yielding will take place thereby protecting the workpiece and preventingthe tool from damaging itself. In the present instance this isaccomplished by providing a ball and socket connection between thepitman rod 52 and the slide and by seating the ball in its socket with ayieldable coil spring. Referring to FIG. 1, the shank 33 of the slide ismade hollow but is necked down as indicated at 81 to provide a seat forthe ball 82 at the outer end of the pitman rod 52. Pressing against theball 82 is a coil spring 83 which is prestressed to provide asubstantial normal force against the pitman rod so that, under normaloperating conditions, the pitman rod and slide reciprocate back andforth as a unit. However, if the tool is obstructed, the pitman rod 52will simply telescope into the shank of the slide, overcoming the forceof the spring 83 thus preventing the buildup of a force greater thanthat for which the spring has been set. It is one of the features of thepresent tool that the encountering of large forces either intentionallyor accidentally may be tolerated by the tool without any danger ofbending the shaft 13. Thus it is one of the features of the constructionthat in addition to the bearing 14 there is provided what might betermed an outboard bearing 15. Thus the shaft 15 is not subjected to anycantilever forces. Or, stated another way, the eccentric drive mechanismis straddled by anti-friction bearings on each side so that large forcesmay be developed in the drive mechanism without any tendency to bend orotherwise damage the drive shaft.

It is a further detailed feature of the construction that adequatelubrit ation is provided for the relatively inaccessible drive assembly,lubricant being fed downwardly from the end of the drive shaft throughlubricant passageways leading directly to the frictional surfaces. Thusreferring to FIG. 6 it will be noted that a grease fitting 9G isprovided at the upper end of the shaft 13 which fitting communicateswith a central bore 91 which is connected to a transverse bore 92 whichleads to the inside of the eccentric sleeve 55. The sleeve is internallygrooved and provided with radial parts 93 so that lubricant passesthrough to the outside of the sleeve. It is found in practice thatoccasional application of a grea e gun to the fitting 99 is adequate toproduce lubrication for several hours of continuous use. For the purposeof lubricating the slide 31, an oil hole 95 is provided in the wall ofthe offset and into which a few drops of oil may be added from time totime. In order to prevent the entry of grit or other foreign material,the oil hole 95 is normally covered by means of an embracing 0 spring96. The ball bearings are of the permanently lubricated type.

Having understood the above construction, it will be apparent to oneskilled in the art that a minimum vibration condition is achievedregardless of the stroke adjustment. Consequently the tool may beoperated for several hours at a stretch or even over an entire shiftwithout the vibration producing any fatigue on the part of the operator.Because of the wide range of stroke adjustment, it has been found thattools of the present design may be used universally in all filing anddie sinking operations, all the way from coarse filing operations to thefinest degree of polishing. Adjustment of the tool is simple andfoolproof since only one adjustment is required to bring about a changein the throw and counterweighting suitable for such throw. The tool issafe since all of the vibrating elements with the exception of the fileitself are completely enclosed and since the tool includes provision forautomatically relieving any overload condition caused by the filestriking an obstruction as it is guided over the work. Finally it willbe apparent that the tool consists of only a small number of movingparts and may be inexpensively constructed while nevertheless ofinherently durable long lasting design.

The tool may be easily disassembled when maintenance or inspectionbecome necessary. Upon removing the shank 48 of the file, the setscrewwhich retains the spring 83 is exposed when the screw is removed, thespring 83 slips out following which a screwdriver may be inserted intothe slotted end of the pitman rod 52. The pitman rod is then unscrewed,following which the entire tubular offset 30 may be unscrewed. Theannular bushing 16 surrounding the upper bearing is next unscrewed,following which the drive shaft 13 and eccentric drive assembly may bewithdrawn from the frame. Assembly following maintenance is equallysimple.

While the tool has been described in connection with the reciprocatingof a file in the form of a block of abrasive, it will be understood thatthe tool is not limited to use with a file and may, if desired, be usedwith a saw tip, a lap charged with abrasive, a felt polishing pad, abrush, or the like.

I claim as my invention:

1. In a power tool or the like the combination comprising a hollowframe, a drive shaft extending longitudinally in said frame, aneccentric on said drive shaft, a

slide having chuck means and mounted in said frame for reciprocatingmovement at right angles to the shaft, a pitman coupled to said slideand having a ring at one end thereof, an eccentric sleeve snuglyinterposed between the eccentric and the ring on the pitman and soarranged that rotating the sleeve causes the throw of the ring withrespect to the shaft to vary from maximum to substantially zero, acounterweight fixed to said shaft, a second counterweight keyed to thesleeve for movement with the sleeve and having means for fixing the samein an adjusted phase position on said shaft, said counterweights beingso phased with respect to their respectively associated shaft and sleeveso that the counterweights are alined for additive effect when thesleeve is in its position for maximum throw and diametrically 0pposedwhen the sleeve is in its position of substantially Zero throw with thedegree of counterweighting varying in unison with the throw in theintermediate positions of adjustment.

2. In a power tool or the like the combination comprising a hollowframe, a drive shaft extending longitudinally in said frame, aneccentric on said drive shaft, a slide having chuck means and mounted insaid frame for reciprocating movement at right angles to the shaft, apitman coupled to said slide and having a ring at one end thereof, aneccentric sleeve snugly interposed between the eccentric and the ring onthe pitman and so arranged that rotating the sleeve 180 causes the throwof the ring with respect to the shaft to vary from maximum tosubstantially zero, a counterweight fixed to said shaft, a secondcounterweight keyed to the sleeve for movement with the sleeve andhaving means for fixing the same in an adjusted phase position on saidshaft, said counterweights being so phased with respect to theirrespectively associated shaft and sleeve so that the counterweights arealined for additive effect when the sleeve is in its position formaximum throw and diametrically opposed when the sleeve is in itsposition of substantially Zero throw with the degree of counterweightingvarying in unison with the throw in the intermediate positions ofadjustment, the fixing means of said second counterweight comprising aset screw, and said hollow frame having an aperture on one side thereoffor receiving a tool so that the set screw can be operated only when thesecond counterweight and sleeve are in a particular registered phaseposition with respect to the frame, and cooperating indicia on the shaftand frame for reading when the tool is inserted into engagement with theset screw for indicating the degree of throw.

References Cited in the file of this patent UNITED STATES PATENTS306,972 Stiles Oct. 21, 1884 1,047,889 Gooch Dec. 17, 1912 1,565,264Dubi Dec. 15, 1925 2,561,344 Cutler July 24, 1951 FOREIGN PATENTS1,018,884 France Jan. 14, 1953 1,084,789 France Jan. 24, 1955 682,278Germany Oct. 11, 1939 709,853 Great Britain June 2, 1954

